Mask



FIG. 1 is a front perspective view of a mask according to our design;

FIG. 2 is a front view thereof;

FIG. 3 is a rear view thereof;

FIG. 4 is a top view thereof;

FIG. 5 is a bottom view thereof; and,

FIG. 6 is a right side view thereof with the left side view being a mirror image. 

CLAIM The ornamental design for a mask, as shown. 